1. Field of the Invention
The present invention relates generally to surgical cutting instruments and, more particularly, to surgical cutting instruments having a tubular inner member with a cutting tip at a distal end rotatably disposed within a tubular outer member with a cutting window at a distal end which cooperates with or permits the cutting tip at the distal end of the inner member to cut or abrade bodily tissue.
2. Discussion of the Related Art
Surgical cutting instruments in which an elongate inner member is rotated within an elongate, tubular outer member have become well accepted in surgical procedures where access to the surgical site is gained via a narrow portal or passage. Typically, the tubular outer member includes a distal end with an opening defining a cutting port or window and the inner member includes a distal end with a cutting tip for engaging bodily tissue via the opening. Proximal ends of the inner and outer members commonly include hubs which attach to a handpiece having a motor for rotating the inner member relative to the outer member. The distal end of the inner member can have various configurations dependent upon the surgical procedure to be performed, with the opening in the distal end of the outer member being suitably configured to cooperate with the particular configuration of the distal end of the inner member to cut, resect or abrade tissue. Often the inner member is tubular so that the loose tissue resulting from a cutting, resecting or abrading procedure can be aspirated through the hollow lumen of the inner member. It is also common for the direction of rotation of the inner member to be reversible during operation. An example of a rotary tissue cutting instrument of the aforementioned type is described in U.S. Pat. No. 4,203,444 to Bonnell et al for use in performing arthroscopic knee surgery.
The tubular inner and outer members disclosed in the Bonnell et al patent are straight. In many surgical procedures, however, it is desirable for the cutting instruments to be bent or curved to access surgical sites which are generally not accessible with straight cutting instruments. For example, in arthroscopic knee surgery it is well known to use curved cutting instruments which can be positioned at various desired angles relative to the surface of the patella. While rotary tissue cutting instruments with curved or bendable shafts have been used for some time, as exemplified by U.S. Pat. No. 4,466,429 to Loscher et al. and U.S. Pat. No. 4,445,509 to Auth, these shafts typically employ a single spirally wound strip of material to impart flexibility while transmitting torque. Unfortunately, spirally wound shafts and couplings tend to unwind when rotated in a direction opposite their winding so that torque can only be transmitted efficiently in one direction.
This problem is addressed in U.S. Pat. No. 177,490 to Fones et al wherein a flexible shaft for transmitting torque in both directions is disclosed having a plurality of coaxial spirally wound strips of material wound in alternating opposite directions relative to one another. U.S. Pat. No. 4,646,738 to Trott describes a rotary tissue cutting instrument for arthroscopic surgery which is similar to the instrument described in the Bonnell et al patent but with a flexible transmission element of the type disclosed in the Fones et al patent. The flexible transmission element of Trott is made up of three coaxial spirally wound strips of material interposed between separate proximal and distal end portions of the inner member to allow the inner member to bend. Proximal and distal end portions of the inner member include reduced diameter neck portions which are telescopically received within the innermost spiral strip to facilitate welding of the strips to the other components of the inner member. Disadvantages of this arrangement include the neck portions tending to stiffen the spiral strips in the vicinity of the cutting tip thereby preventing the inner member from bending adjacent the cutting tip and the inner member having an increased diameter. In addition, it is possible for the separate components to become detached from one another during use such that torque can no longer be effectively transmitted to the cutting tip.
Accordingly, it is a primary object of the present invention to overcome the abovementioned disadvantages of the prior art and to improve angled rotary tissue cutting instruments used in surgery of the head and neck and other parts of the body.
It is another object of the present invention to reduce the number of parts needed to form an angled rotary tissue cutting instrument with tubular inner and outer members by forming a tubular portion of the inner member as an integral one-piece unit and creating a spiral cut in the tubular portion in a region adjacent a bend in the outer member.
It is yet another object of the present invention to improve access in head and neck surgery by providing an angled rotary tissue cutting instrument with a bend in an outer member immediately adjacent a cutting tip at a distal of an inner member disposed within the outer member.
Still another object of the present invention is to facilitate bending of an angled rotary tissue cutting instrument immediately adjacent the cutting tip by forming the inner member with a spiral cut which extends from a proximal portion of the inner member to the cutting tip.
The present invention is generally characterized in an angled rotary tissue cutting instrument including an outer member including a rigid tube having proximal and distal portions connected by a bend and a cutting window defined at a distal end of the tube, and an inner member rotatably disposed within the outer member and including an inner tube of integral one-piece construction with a helical cut formed therein in a first direction to define a flexible region adjacent the bend, a cutting tip disposed at a distal end of the inner tube adjacent the cutting window, and a first strip of material spirally wound over the helical cut in a second direction opposite the first direction. In a preferred embodiment, a second strip of material is spirally wound over the first strip of material in the first direction, with opposite ends of the first and second strips of material being secured to the inner tube on opposite sides of the helical cut.
Another aspect of the present invention is generally characterized in a method of fabricating an angled rotary tissue cutting instrument including the steps of producing an inner member by forming a helical cut in a first direction around an inner tube, forming a cutting tip at a distal end of the inner tube, and wrapping a first strip of material spirally over the helical cut in a second direction opposite the first direction, the inner member being inserted into the outer tube of an outer member such that the cutting tip is disposed adjacent a cutting window at the distal end of the outer tube, and bending the outer member in the vicinity of the helical cut in the inner tube. A second strip of material can also be wrapped spirally over the first strip of material in the first direction. Preferably, opposite ends of the first and second strips of material are secured to the inner tube on opposite sides of the helical cut.
Some of the advantages of the present invention over the prior art are that the number of parts needed to produce an angled rotary tissue cutting instrument are reduced, that the angled rotary tissue cutting instrument can be bent closer to the distal end or tip of the instrument to improve access in surgery of the head and neck and other parts of the body, that the size or diameter of the instrument can be minimal to increase use and access, that the inner member has a configuration to accommodate flow of irrigating fluid to the distal end, and that the strength of the flexible inner member is increased.